An important factor which limits the expanded use of legumes as a source of protein in the human diet is the relatively poor availability of its amino acids, an effect which is particularly significant with respect to the S-containing amino acids since these constitute the limiting amino acids of most legume proteins. The broad objectives of this research are two-fold: (1) to find the causes for the poor availability of amino acids from legume proteins, and (2) to explore practical means whereby this limitation can be overcome. After determining the in vivo and in vitro digestibility of a number of food legumes, an attempt will be made to isolate the enzyme-resistant protein fraction responsible for the poor digestibility observed in such systems. This protein will be characterized with respect to amino acid composition and carbohydrate to see if these properties might not give some clue for their resistance to enzyme attack; its identification in disc gel electrophoretic patterns may present the possibility of using this as a screening technique for the plant breeder. Enzymatic and chemical modification of the enzyme-resistant protein will be tried to see if such treatment enhances the digestibility of the protein.